LTM8057
3.1VIN to 31VIN Isolated
µModule DC/DC Converter
FEATURES
DESCRIPTION
n
n
n
The LTM®8057 is a 2kV AC isolated flyback µModule®
(micromodule) DC/DC converter. Included in the package
are the switching controller, power switches, transformer,
and all support components. Operating over an input voltage range of 3.1V to 31V, the LTM8057 supports an output
voltage range of 2.5V to 12V, set by a single resistor. Only
output and input capacitors are needed to finish the design.
Other components may be used to control the soft-start
control and biasing.
n
n
n
n
n
2kV AC Isolated µModule Converter (Tested at 3kVDC)
UL60950 Recognized File 464570
Wide Input Voltage Range: 3.1V to 31V
Up to 440mA Output Current (VIN = 24V, VOUT1 = 2.5V)
Output Adjustable from 2.5V to 12V
Current Mode Control
Programmable Soft-Start
User Configurable Undervoltage Lockout
Low Profile (9mm × 11.25mm × 4.92mm)
BGA Package
APPLICATIONS
Industrial Sensors
Industrial Switches
n Test and Measurement Equipment
n
n
The LTM8057 is packaged in a thermally enhanced, compact (9mm × 11.25mm × 4.92mm) overmolded ball grid
array (BGA) package suitable for automated assembly
by standard surface mount equipment. The LTM8057 is
available with SnPb or RoHS compliant terminal finish.
L, LT, LTC, LTM, Linear Technology, the Linear logo and µModule are registered trademarks of
Analog Devices, Inc. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
2kV AC Isolated µModule Regulator
VOUT
VOUT
5V
•
RUN
•
2.2µF
22µF
VOUT–
GND
BIAS
4.7µF
6.98k
SS
ADJ
LTM8057
2kV AC ISOLATION
8057 TA01a
400
MAXIMUM OUTPUT CURRENT (mA)
VIN
VIN
4.3V TO 29V
Maximum Output Current vs VIN
300
200
100
0
0
5
10
15
VIN (V)
20
25
30
8057 TA01b
8057fa
For more information www.linear.com/LTM8057
1
LTM8057
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
TOP VIEW
VIN, RUN, BIAS .........................................................32V
ADJ, SS........................................................................5V
VOUT1 Relative to VOUT–.............................................16V
VIN + VOUT (Note 2)....................................................36V
BIAS Above VIN......................................................... 0.1V
GND to VOUT– Isolation (Note 3).......................... 2kV AC
Maximum Internal Temperature (Note 4)............... 125°C
Peak Solder Reflow Body Temperature.................. 245°C
Storage Temperature.............................. –55°C to 125°C
A
B
BANK 1
VOUT
BANK 2
VOUT–
C
D
E
F
BANK 5
VIN
G
BANK 4
GND
RUN
H
ADJ
BIAS SS
1
3
4
5
6
7
BGA PACKAGE
38-LEAD (11.25mm × 9mm × 4.92mm)
TJMAX = 125°C, θJA = 16°C/W, θJCbottom = 4.1°C/W, θJCtop = 15°C/W, θJB = 4°C/W
WEIGHT = 1.1g, θ VALUES DETERMINED PER JEDEC 51-9, 51-12
ORDER INFORMATION
2
http://www.linear.com/product/LTM8057#orderinfo
PART MARKING*
PAD OR BALL FINISH
DEVICE
CODE
PACKAGE
TYPE
MSL
RATING
LTM8057EY#PBF
SAC305 (RoHS)
LTM8057Y
e1
BGA
3
–40°C to 125°C
LTM8057IY#PBF
SAC305 (RoHS)
LTM8057Y
e1
BGA
3
–40°C to 125°C
PART NUMBER
LTM8057IY
LTM8057MPY#PBF
LTM8057MPY
TEMPERATURE RANGE (SEE NOTE 4)
SnPb (63/37)
LTM8057Y
e0
BGA
3
–40°C to 125°C
SAC305 (RoHS)
LTM8057Y
e1
BGA
3
–55°C to 125°C
SnPb (63/37)
LTM8057Y
e0
BGA
3
–55°C to 125°C
Consult Marketing for parts specified with wider operating temperature
ranges. *Device temperature grade is indicated by a label on the shipping
container. Pad or ball finish code is per IPC/JEDEC J-STD-609.
• Recommended LGA and BGA PCB Assembly and Manufacturing
Procedures:
www.linear.com/umodule/pcbassembly
• Terminal Finish Part Marking:
www.linear.com/leadfree
• LGA and BGA Package and Tray Drawings:
www.linear.com/packaging
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LTM8057
ELECTRICAL
CHARACTERISTICS
The
l denotes the specifications which apply over the full internal
operating temperature range, otherwise specifications are at TA = 25°C, RUN = 12V (Note 4).
PARAMETER
CONDITIONS
Minimum Input DC Voltage
BIAS = VIN, RUN = 2V
BIAS Open, RUN = 2V
l
l
MIN
VOUT DC Voltage
RADJ = 12.4k
RADJ = 6.98k
RADJ = 3.16k
l
4.75
TYP
2.5
5
12
VIN Quiescent Current
VRUN = 0V
Not Switching
850
VOUT Line Regulation
6V ≤ VIN ≤ 31V, IOUT = 0.15A, RUN = 2V
1.7
MAX
UNITS
3.1
4.3
V
V
5.25
V
V
V
1
µA
µA
%
VOUT Load Regulation
0.05A ≤ IOUT ≤ 0.2A, RUN = 2V
1.5
%
VOUT Ripple (RMS)
IOUT = 0.1A, 1MHz BW
20
mV
Isolation Test Voltage
(Note 3)
Input Short-Circuit Current
VOUT Shorted
RUN Pin Input Threshold
RUN Pin Rising
RUN Pin Current
VRUN = 1V
VRUN = 1.3V
3000
30
1.18
SS Threshold
SS Sourcing Current
SS = 0V
BIAS Current
VIN = 12V, BIAS = 5V, ILOAD = 100mA
Minimum BIAS Voltage (Note 5)
ILOAD = 100mA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: VIN + VOUT is defined as the sum of (VIN – GND) + (VOUT – VOUT–).
Note 3: The LTM8057 isolation is tested at 3kV DC for one second.
Note 4: The LTM8057E is guaranteed to meet performance specifications
from 0°C to 125°C. Specifications over the –40°C to 125°C internal
temperature range are assured by design, characterization and correlation
with statistical process controls. LTM8057I is guaranteed to meet
V DC
1.24
mA
1.30
V
2.5
0.1
µA
µA
0.7
V
–10
µA
9
mA
3.1
V
specifications over the full –40°C to 125°C internal operating temperature
range. The LTM8057MP is guaranteed to meet specifications over the
full –55°C to 125°C internal operating temperature range. Note that
the maximum internal temperature is determined by specific operating
conditions in conjunction with board layout, the rated package thermal
resistance and other environmental factors.
Test flowcharts are posted for viewing at:
www.linear.com/quality
Note 5: This is the BIAS pin voltage at which the internal circuitry is
powered through the BIAS pin and not the integrated regulator. See BIAS
Pin Considerations for details.
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3
LTM8057
TYPICAL PERFORMANCE CHARACTERISTICS
as in Table 1 (TA = 25°C).
VOUT = 2.5V
BIAS = 5V
Efficiency vs Output Current
80
12VIN
EFFICIENCY (%)
EFFICIENCY (%)
24VIN
65
60
55
50
VOUT = 3.3V
BIAS = 5V
75
70
Efficiency vs Output Current
80
70
24VIN
65
60
55
200
100
300
OUTPUT CURRENT (mA)
0
50
400
100
200
300
OUTPUT CURRENT (mA)
0
12VIN
Input Current vs Output Current
VOUT = 2.5V
80 BIAS = 5V
12VIN
65
24VIN
70
65
60
60
55
55
400
90
75
70
100
200
300
OUTPUT CURRENT (mA)
0
8057 G03
VOUT = 12V
BIAS = 5V
80
24VIN
EFFICIENCY (%)
EFFICIENCY (%)
60
Efficiency vs Output Current
85
75
65
50
400
INPUT CURRENT (mA)
80
24VIN
70
8057 G02
Efficiency vs Output Current
VOUT = 8V
BIAS = 5V
12VIN
55
8057 G01
85
VOUT = 5V
BIAS = 5V
75
12VIN
EFFICIENCY (%)
Efficiency vs Output Current
75
Unless otherwise noted, operating conditions are
70
12VIN
60
50
24VIN
40
30
20
50
0
50
200
150
250
100
OUTPUT CURRENT (mA)
50
300
10
50
100
8057 G04
12VIN
70
60
24VIN
50
40
30
20
100
12VIN
80
24VIN
60
40
20
10
0
8057 G06
VOUT = 5V
BIAS = 5V
120
INPUT CURRENT (mA)
INPUT CURRENT (mA)
80
400
Input Current vs Output Current
140
VOUT = 3.3V
BIAS = 5V
90
200
100
300
OUTPUT CURRENT (mA)
1
8057 G05
Input Current vs Output Current
100
0
200
150
OUTPUT CURRENT (mA)
0
0
200
100
300
OUTPUT CURRENT (mA)
400
0
0
8057 G07
100
200
300
OUTPUT CURRENT (mA)
400
8057 G08
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LTM8057
TYPICAL
PERFORMANCE CHARACTERISTICS
as in Table 1 (TA = 25°C).
Input Current vs Output Current
180
VOUT = 2.5V
8 BIAS = 5V
VOUT = 12V
BIAS = 5V
180
24VIN
80
60
7
140
BIAS CURRENT (mA)
100
INPUT CURRENT (mA)
12VIN
120
12VIN
120
100
24VIN
80
60
5
3
40
2
20
1
50
100
150
200
250
OUTPUT CURRENT (mA)
0
300
12
VOUT = 3.3V
BIAS = 5V
VOUT = 5V
BIAS = 5V
BIAS CURRENT (mA)
24VIN
6
5
4
3
2
12VIN
8
24VIN
6
4
24VIN
6
4
2
0
400
200
100
300
OUTPUT CURRENT (mA)
100
200
500
MAXIMUM OUTPUT CURRENT (mA)
VOUT = 12V
BIAS = 5V
12
12VIN
10
24VIN
8
6
4
2
0
0
50
100
0
50
100
150
200
250
OUTPUT CURRENT (mA)
8057 G13
Bias Current vs Output Current
14
0
400
300
OUTPUT CURRENT (mA)
0
8057 G12
BIAS CURRENT (mA)
0
12VIN
8
2
1
VOUT = 8V
BIAS = 5V
10
10
12VIN
7
0
Bias Current vs Output Current
12
BIAS CURRENT (mA)
8
400
8057 G11
Bias Current vs Output Current
Bias Current vs Output Current
9
200
100
300
OUTPUT CURRENT (mA)
1
8057 G10
8057 G09
10
0
200
100
50
150
OUTPUT CURRENT (mA)
0
24VIN
4
20
0
12VIN
6
40
0
BIAS CURRENT (mA)
Bias Current vs Output Current
9
160
140
INPUT CURRENT (mA)
Input Current vs Output Current
200
VOUT = 8V
BIAS = 5V
160
Unless otherwise noted, operating conditions are
150
OUTPUT CURRENT (mA)
200
300
8057 G14
Maximum Output Current vs VIN
BIAS = 5V FOR VIN ≥ 5V
BIAS = VIN FOR VIN < 5V
400
300
200
100
0
VOUT = 2.5V
VOUT = 3.3V
VOUT = 5V
0
8057 G15
5
10
15
VIN (V)
20
25
30
8057 G16
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5
LTM8057
TYPICAL
PERFORMANCE CHARACTERISTICS
Unless otherwise noted, operating conditions are
as in Table 1 (TA = 25°C).
Maximum Output Current vs VIN
45
300
200
100
0
VOUT = 8V
VOUT = 12V
0
5
10
15
VIN (V)
25
20
40
35
30
25
20
15
10
VOUT = 2.5V
VOUT = 3.3V
VOUT = 5V
5
0
30
25
BIAS = 5V FOR VIN ≥ 5V
BIAS = VIN FOR VIN < 5V
MINIMUM REQUIRED LOAD (mA)
BIAS = 5V FOR VIN ≥ 5V
BIAS = VIN FOR VIN < 5V
MAXIMUM REQUIRED LOAD (mA)
MAXIMUM OUTPUT CURRENT (mA)
400
Minimum Required Load
vs Input Voltage
Minimum Required Load
vs Input Voltage
0
20
10
20
15
10
5
0
40
30
INPUT VOLTAGE (V)
8057 G18
8057 G17
Typical Output Ripple
100mA Output Current, VIN = 12V
BIAS = 5V FOR VIN ≥ 5V
BIAS = VIN FOR VIN < 5V
DC1988 VOUT1 Start-Up Behavior
for Different CSS Values
VOUT1 = 8V
VOUT1 = 12V*
0
25
30
10
15
20
INPUT VOLTAGE (V)
8057 G19
*SEE APPLICATIONS INFORMATION SECTION
FOR DISCUSSION OF 12VOUT MINIMUM LOAD
5
Typical Switching Frequency vs
Output Current Stock DC1988A
900
NO CSS
800
5mV/DIV
CSS = 0.1µF
1V/DIV
8057 G20
500ns/DIV
MEASURED ON DC1987 WITH ADDIONAL 1µF
AND BNC ATTACHED TO OUTPUT TERMINALS.
C7 = 0.1µF. USED HP461A 150MHz AMPLIFIER,
SET TO 40dB GAIN.
SWITCHING FREQUENCY (kHz)
CSS = 0.01µF
8057 G21
200µs/DIV
100mA RESISTIVE LOAD
700
12VIN
600
500
5VIN
400
300
200
100
0
0
50
200
150
100
OUTPUT CURRENT (mA)
250
8057 G22
Junction Temperature Rise
vs Load Current
80
8
70
7
TEMPERATURE RISE (°C)
INPUT CURRENT (mA)
Input Current
vs VIN, VOUT Shorted
60
50
40
30
20
10
VOUT = 2.5V
6
5
4
3
2
3.3VIN
5VIN
12VIN
24VIN
1
0
4
8
12
16 20
VIN (V)
24
28
32
0
0
50
8057 G23
100 150 200 250 300 350 400
VOUT LOAD CURRENT (mA)
8057 G24
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LTM8057
TYPICAL
PERFORMANCE CHARACTERISTICS
Unless otherwise noted, operating conditions are
as in Table 1 (TA = 25°C).
Junction Temperature Rise
vs Load Current
9
10
VOUT = 3.3V
7
6
5
4
3
3.3VIN
5VIN
12VIN
24VIN
2
1
0
0
50
VOUT = 5V
9
TEMPERATURE RISE (°C)
8
TEMPERATURE RISE (°C)
Junction Temperature Rise
vs Load Current
8
7
6
5
4
3
3.3VIN
5VIN
12VIN
24VIN
2
1
0
100 150 200 250 300 350 400
VOUT LOAD CURRENT (mA)
0
50
8057 G25
Junction Temperature Rise
vs Load Current
12
VOUT = 8V
VOUT = 12V
10
8
6
4
3.3VIN
5VIN
12VIN
24VIN
2
0
50
100
150
200
250
VOUT LOAD CURRENT (mA)
300
TEMPERATURE RISE (°C)
TEMPERATURE RISE (°C)
10
0
350
8057 G26
Junction Temperature Rise
vs Load Current
12
100 150 200 250 300
VOUT LOAD CURRENT (mA)
8
6
4
3.3VIN
5VIN
12VIN
24VIN
2
0
0
8057 G27
50
100
150
200
VOUT LOAD CURRENT (mA)
250
8057 G28
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7
LTM8057
PIN FUNCTIONS
PACKAGE ROW AND COLUMN LABELING MAY VARY
AMONG µModule PRODUCTS. REVIEW EACH PACKAGE
LAYOUT CAREFULLY.
VOUT (Bank 1): VOUT and VOUT– comprise the isolated
output of the LTM8057 flyback stage. Apply an external
capacitor between VOUT and VOUT–. Do not allow VOUT– to
exceed VOUT.
VOUT– (Bank 2): VOUT– is the return for both VOUT1 and
VOUT2. VOUT1 and VOUT– comprise the isolated output of
the LTM8057. In most applications, the bulk of the heat
flow out of the LTM8057 is through the GND and VOUT–
pads, so the printed circuit design has a large impact on
the thermal performance of the part. See the PCB Layout
and Thermal Considerations sections for more details.
Apply an external capacitor between VOUT and VOUT–.
GND (Bank 4): This is the primary side local ground of the
LTM8057 primary. In most applications, the bulk of the heat
flow out of the LTM8057 is through the GND and VOUT–
pads, so the printed circuit design has a large impact on
the thermal performance of the part. See the PCB Layout
and Thermal Considerations sections for more details.
VIN (Bank 5): VIN supplies current to the LTM8057’s internal regulator and to the integrated power switch. These
pins must be locally bypassed with an external, low ESR
capacitor.
RUN (Pin F3): A resistive divider connected to VIN and this
pin programs the minimum voltage at which the LTM8057
will operate. Below 1.24V, the LTM8057 does not deliver
power to the secondary. Above 1.24V, power will be delivered to the secondary and 10µA will be fed into the SS
pin. When RUN is less than 1.24V, the pin draws 2.5µA,
allowing for a programmable hysteresis. Do not allow a
negative voltage (relative to GND) on this pin. Tie this pin
to VIN if it is not used.
ADJ (Pins G7): Apply a resistor from this pin to GND to
set the output voltage VOUT1 relative to VOUT–, using the
recommended value given in Table 1. If Table 1 does not
list the desired VOUT value, the equation:
(
)
R ADJ = 28.4 VOUT1–0.879 kΩ
may be used to approximate the value. To the seasoned
designer, this exponential equation may seem unusual. The
equation is exponential due to nonlinear current sources
that are used to temperature compensate the regulation.
BIAS (Pin H5): This pin supplies the power necessary to
operate the LTM8057. It must be locally bypassed with a
low ESR capacitor of at least 4.7μF. Do not allow this pin
voltage to rise above VIN.
SS (Pin H6): Place a soft-start capacitor here to limit inrush
current and the output voltage ramp rate. Do not allow a
negative voltage (relative to GND) on this pin.
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LTM8057
BLOCK DIAGRAM
VOUT
VIN
•
•
0.1µF
1µF
RUN
BIAS*
SS
VOUT–
CURRENT
MODE
CONTROLLER
ADJ
GND
8057 BD
*DO NOT ALLOW BIAS VOLTAGE TO BE ABOVE VIN
OPERATION
The LTM8057 is a stand-alone isolated flyback switching
DC/DC power supply that can deliver up to 440mA of output
current. This module provides a regulated output voltage
programmable via one external resistor from 2.5V to 12V.
The input voltage range of the LTM8057 is 3.1V to 31V.
Given that the LTM8057 is a flyback converter, the output
current depends upon the input and output voltages, so
make sure that the input voltage is high enough to support
the desired output voltage and load current. The Typical
Performance Characteristics section gives several graphs
of the maximum load versus VIN for several output voltages.
A simplified block diagram is given. The LTM8057 contains
a current mode controller, power switching element, power
transformer, power Schottky diode and a modest amount
of input and output capacitance.
The LTM8057 has a galvanic primary to secondary isolation rating of 2kV AC. This is verified by applying 3kV DC
between the primary and secondary for 1 second. Note that
the 2kV AC isolation is verified by a 3kV DC test. The peak
voltage of a 2kV AC waveform is 2.83kV DC, so 3kV DC is
applied. For details please refer to the Isolation, Working
Voltage and Safely Compliance section. The LTM8057 is
a UL 60950 recognized component.
An internal regulator provides power to the control circuitry. The bias regulator normally draws power from the
VIN pin, but if the BIAS pin is connected to an external
voltage higher than 3.1V, bias power will be drawn from
the external source, improving efficiency. VBIAS must not
exceed VIN. The RUN pin is used to turn on or off the
LTM8057, disconnecting the output and reducing the input
current to 1μA or less.
The LTM8057 is a variable frequency device. For a fixed
input and output voltage, the frequency increases as the
load increases. For light loads, the current through the
internal transformer may be discontinuous.
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9
LTM8057
APPLICATIONS INFORMATION
For most applications, the design process is straight
forward, summarized as follows:
1. Look at Table 1a and find the row that has the desired
input range and output voltage.
2. Apply the recommended CIN, COUT and RADJ if required.
3. Connect BIAS as indicated, or tie to an external source
up to 15V or VIN, whichever is less.
While these component combinations have been tested for
proper operation, it is incumbent upon the user to verify
proper operation over the intended system’s line, load and
environmental conditions. Bear in mind that the maximum
output current may be limited by junction temperature,
the relationship between the input and output voltage
magnitude and polarity and other factors. Please refer
to the graphs in the Typical Performance Characteristics
section for guidance.
Capacitor Selection Considerations
The CIN and COUT capacitor values in Table 1 are the
minimum recommended values for the associated operating conditions. Applying capacitor values below those
indicated in Table 1 is not recommended, and may result
in undesirable operation. Using larger values is generally
acceptable, and can yield improved dynamic response, if
it is necessary. Again, it is incumbent upon the user to
verify proper operation over the intended system’s line,
load and environmental conditions.
Ceramic capacitors are small, robust and have very low
ESR. However, not all ceramic capacitors are suitable.
X5R and X7R types are stable over temperature and applied voltage and give dependable service. Other types,
including Y5V and Z5U have very large temperature and
voltage coefficients of capacitance. In an application circuit they may have only a small fraction of their nominal
capacitance resulting in much higher output voltage ripple
than expected.
A final precaution regarding ceramic capacitors concerns
the maximum input voltage rating of the LTM8057. A
ceramic input capacitor combined with trace or cable
inductance forms a high-Q (underdamped) tank circuit. If
the LTM8057 circuit is plugged into a live supply, the input
voltage can ring to much higher than its nominal value,
possibly exceeding the device’s rating. This situation is
easily avoided; see the Hot-Plugging Safely section.
LTM8057 Table 1a. Recommended Component Values and Configuration for Specific VOUT Voltages (TA = 25°C)
VIN
VOUT
VBIAS
CIN
COUT
RADJ
3.1V to 31V
2.5V
3.1V to 15V or Open
2.2µF, 50V, 1206
100µF, 6.3V, 1210
12.4k
3.1V to 31V
3.3V
3.1V to 15V or Open
2.2µF, 50V, 1206
100µF, 6.3V, 1210
10k
3.1V to 29V
5V
3.1V to 15V or Open
2.2µF, 50V, 1206
22µF, 16V, 1210
6.98k
3.1V to 26V
8V
3.1V to 15V or Open
2.2µF, 50V, 1206
22µF, 10V, 1206
4.53k
3.1V to 24V
12V
3.1V to 15V or Open
2.2µF, 25V, 0805
10µF, 16V, 1210
3.16k/8.2pF*
9V to 15V
2.5V
VIN
2.2µF, 50V, 1206
100µF, 6.3V, 1210
12.4k
9V to 15V
3.3V
VIN
2.2µF, 50V, 1206
47µF, 6.3V, 1210
10k
9V to 15V
5V
VIN
2.2µF, 50V, 1206
22µF, 16V, 1210
6.98k
9V to 15V
8V
VIN
2.2µF, 50V, 1206
22µF, 10V, 1206
4.53k
9V to 15V
12V
VIN
2.2µF, 25V, 0805
10µF, 16V, 1210
3.16k
18V to 31V
2.5V
3.1V to 15V or Open
2.2µF, 50V, 1206
100µF, 6.3V, 1210
12.4k
18V to 31V
3.3V
3.1V to 15V or Open
2.2µF, 50V, 1206
47µF, 6.3V, 1210
10k
18V to 29V
5V
3.1V to 15V or Open
2.2µF, 50V, 1206
22µF, 16V, 1210
6.98k
18V to 26V
8V
3.1V to 15V or Open
2.2µF, 50V, 1206
22µF, 10V, 1206
4.53k
18V to 24V
12V
3.1V to 15V or Open
2.2µF, 50V, 1206
10µF, 16V, 1210
3.16k/8.2pF*
Note: Do not allow BIAS to exceed VIN, a bulk input capacitor is required. If BIAS is open, the minimum VIN is 4.3V.
*Connect 3.16k in parallel with 8.2pF from ADJ to GND
8057fa
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For more information www.linear.com/LTM8057
LTM8057
APPLICATIONS INFORMATION
BIAS Pin Considerations
The BIAS pin is the output of an internal linear regulator
that powers the LTM8057’s internal circuitry. It is set to
3V and must be decoupled with a low ESR capacitor of at
least 4.7μF. The LTM8057 will run properly without applying
a voltage to this pin, but will operate more efficiently and
dissipate less power if a voltage between 3.1V and VIN is
applied. At low VIN, the LTM8057 will be able to deliver
more output current if BIAS is 3.1V or greater. Up to 31V
may be applied to this pin, but a high BIAS voltage will
cause excessive power dissipation in the internal circuitry.
For applications with an input voltage less than 15V, the
BIAS pin is typically connected directly to the VIN pin. For
input voltages greater than 15V, it is preferred to leave the
BIAS pin separate from the VIN pin, either powered from
a separate voltage source or left running from the internal
regulator. This has the added advantage of keeping the
physical size of the BIAS capacitor small. Do not allow
BIAS to rise above VIN.
Soft-Start
For many applications, it is necessary to minimize the
inrush current at start-up. The built-in soft-start circuit
significantly reduces the start-up current spike and output
voltage overshoot by applying a capacitor from SS to GND.
When the LTM8057 is enabled, whether from VIN reaching
a sufficiently high voltage or RUN being pulled high, the
LTM8057 will source approximately 10µA out of the SS
pin. As this current gradually charges the capacitor from
SS to GND, the LTM8057 will correspondingly increase
the power delivered to the output, allowing for a graceful
turn-on ramp.
Isolation, Working Voltage and Safety Compliance
The LTM8057 isolation is 100% hi-pot tested by tying all of
the primary pins together, all of the secondary pins together
and subjecting the two resultant circuits to a differential
of 3kV DC for one second. This establishes the isolation
voltage rating of the LTM8057 component.
The isolation rating of the LTM8057 is not the same as
the working or operational voltage that the application
will experience. This is subject to the application’s power
source, operating conditions, the industry where the end
product is used and other factors that dictate design requirements such as the gap between copper planes, traces
and component pins on the printed circuit board, as well
as the type of connector that may be used. To maximize
the allowable working voltage, the LTM8057 has two
columns of solder balls removed to facilitate the printed
circuit board design. The ball to ball pitch is 1.27mm, and
the typical ball diameter is 0.78mm. Accounting for the
missing columns and the ball diameter, the printed circuit
board may be designed for a metal-to-metal separation of
up to 3.03mm. This may have to be reduced somewhat to
allow for tolerances in solder mask or other printed circuit
board design rules. For those situations where information about the spacing of LTM8057 internal circuitry is
required, the minimum metal to metal separation of the
primary and secondary is 0.75mm.
To reiterate, the manufacturer’s isolation voltage rating
and the required working or operational voltage are often
different numbers. In the case of the LTM8057, the isolation voltage rating is established by 100% hi-pot testing.
The working or operational voltage is a function of the
end product and its system level specifications. The actual required operational voltage is often smaller than the
manufacturer’s isolation rating.
The LTM8057 is a UL recognized component under
UL 60950, file number 464570. The UL 60950 insulation category of the LTM8057 transformer is Functional.
Considering UL 60950 Table 2N and the gap distances
stated above, 3.03mm external and 0.75mm internal,
the LTM8057 may be operated with up to 250V working
voltage in a pollution degree 2 environment. The actual
working voltage, insulation category, pollution degree and
other critical parameters for the specific end application
depend upon the actual environmental, application and
safety compliance requirements. It is therefore up to the
user to perform a safety and compliance review to ensure
that the LTM8057 is suitable for the intended application.
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11
LTM8057
APPLICATIONS INFORMATION
ADJ and Line Regulation
VOUT to VOUT– Reverse Voltage
For VOUT greater than 8V, parasitics in the transformer
interacting with the controller cause a localized increase in
minimum load. A small capacitor may need to be applied
from ADJ to GND to ensure proper line regulation. Care
must be taken when choosing this capacitor value. Too
small or no capacitor will result in poor line regulation;
in general, a larger capacitor is needed for higher VOUT.
Too large of a capacitance will require excessive minimum
load to maintain regulation.
The LTM8057 cannot tolerate a reverse voltage from VOUTto
VOUT– during operation. If VOUT– raises above VOUT during operation, the LTM8057 may be damaged. To protect
against this condition, a low forward drop power Schottky
diode has been integrated into the LTM8057, anti-parallel
to VOUT/VOUT–. This can protect the output against many
reverse voltage faults. Reverse voltage faults can be both
steady state and transient. An example of a steady-state
voltage reversal is accidentally misconnecting a powered
LTM8057 to a negative voltage source. An example of
transient voltage reversals is a momentary connection to
a negative voltage. It is also possible to achieve a VOUTreversal if the load is short circuited through a long cable.
The inductance of the long cable forms an LC tank circuit
with the VOUT capacitance, which drive VOUT negative.
Avoid these conditions.
The plots in Figure 1 show LTM8057 line regulation at
three different capacitor values applied from ADJ to GND.
The plots in Figure 2 show the minimum load requirement
for the same three capacitors.
Carefully choose the appropriate capacitor value for the
intended application.
Safety Rated Capacitors
5
4
3
DEVIATION (%)
2
1
0
–1
–2
–3
NO CAP
8.2pF CAP
12pF CAP
–4
–5
0
6
12
VIN (V)
18
24
8057 F01
Figure 1. VOUT Line Regulation vs VIN
MINIMUM REQUIRED LOAD (mV)
25
BIAS = 5V FOR VIN ≥ 5V
BIAS = VIN FOR VIN < 5V
NO CAP
8.2pF CAP
12pF CAP
20
15
Some applications require safety rated capacitors, which
are high voltage capacitors that are specifically designed
and rated for AC operation and high voltage surges. These
capacitors are often certified to safety standards such as UL
60950, IEC 60950 and others. In the case of the LTM8057,
a common application of a safety rated capacitor would
be to connect it from GND to VOUT–. To provide maximum
flexibility, the LTM8057 does not include any components
between GND and VOUT–. Any safety capacitors must be
added externally.
The specific capacitor and circuit configuration for any
application depends upon the safety requirements of
the system into which the LTM8057 is being designed.
Table 2 provides a list of possible capacitors and their
manufacturers. The application of a capacitor from GND
to VOUT– may also reduce the high frequency output noise
on the output.
10
5
0
0
6
12
INPUT VOLTAGE (V)
18
24
8057 F02
Figure 2. Minimum Required Load vs Input Voltage
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For more information www.linear.com/LTM8057
LTM8057
APPLICATIONS INFORMATION
A few rules to keep in mind are:
Table 2. Safety Rated Capacitors
MANUFACTURER PART NUMBER
DESCRIPTION
Murata
Electronics
GA343DR7GD472KW01L
4700pF, 250V AC, X7R,
4.5mm × 3.2mm
Capacitor
Johanson
Dielectrics
302R29W471KV3E-****-SC 470pF, 250V AC, X7R,
4.5mm × 2mm
Capacitor
Syfer Technology 1808JA250102JCTSP
100pF, 250V AC, C0G,
1808 Capacitor
PCB Layout
Most of the headaches associated with PCB layout have
been alleviated or even eliminated by the high level of
integration of the LTM8057. The LTM8057 is nevertheless a switching power supply, and care must be taken to
minimize electrical noise to ensure proper operation. Even
with the high level of integration, you may fail to achieve
specified operation with a haphazard or poor layout. See
Figure 3 for a suggested layout. Ensure that the grounding
and heat sinking are acceptable.
1. Place the RADJ resistor as close as possible to their
respective pins.
2. Place the CIN capacitor as close as possible to the VIN
and GND connections of the LTM8057.
3. Place the COUT1 capacitor as close as possible to VOUT
and VOUT–.
4. Place the CIN and COUT capacitors such that their
ground current flow directly adjacent or underneath
the LTM8057.
5. Connect all of the GND connections to as large a copper
pour or plane area as possible on the top layer. Avoid
breaking the ground connection between the external
components and the LTM8057.
ADJ
VOUT
LTM8058
SS
COUT1
BIAS
CBIAS
VOUT–
RUN
CIN
VIN
THERMAL/INTERCONNECT VIAS
8057 F03
Figure 3. Layout Showing Suggested External Components, Planes and Thermal Vias
8057fa
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13
LTM8057
APPLICATIONS INFORMATION
6. Use vias to connect the GND copper area to the board’s
internal ground planes. Liberally distribute these GND
vias to provide both a good ground connection and
thermal path to the internal planes of the printed circuit
board. Pay attention to the location and density of the
thermal vias in Figure 3. The LTM8057 can benefit from
the heat sinking afforded by vias that connect to internal
GND planes at these locations, due to their proximity
to internal power handling components. The optimum
number of thermal vias depends upon the printed
circuit board design. For example, a board might use
very small via holes. It should employ more thermal
vias than a board that uses larger holes.
voltage, output power and ambient temperature. The
temperature rise curves given in the Typical Performance
Characteristics section can be used as a guide. These curves
were generated by the LTM8057 mounted to a 58cm2
4-layer FR4 printed circuit board. Boards of other sizes
and layer count can exhibit different thermal behavior, so
it is incumbent upon the user to verify proper operation
over the intended system’s line, load and environmental
operating conditions.
Hot-Plugging Safely
θJA: Thermal resistance from junction to ambient
The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the input
bypass capacitor of the LTM8057. However, these capacitors can cause problems if the LTM8057 is plugged into a
live supply (see Linear Technology Application Note 88 for
a complete discussion). The low loss ceramic capacitor
combined with stray inductance in series with the power
source forms an underdamped tank circuit, and the voltage at the VIN pin of the LTM8057 can ring to more than
twice the nominal input voltage, possibly exceeding the
LTM8057’s rating and damaging the part. If the input
supply is poorly controlled or the user will be plugging
the LTM8057 into an energized supply, the input network
should be designed to prevent this overshoot. This can be
accomplished by installing a small resistor in series to VIN,
but the most popular method of controlling input voltage
overshoot is adding an electrolytic bulk capacitor to the
VIN net. This capacitor’s relatively high equivalent series
resistance damps the circuit and eliminates the voltage
overshoot. The extra capacitor improves low frequency
ripple filtering and can slightly improve the efficiency of the
circuit, though it can be a large component in the circuit.
θJCbottom: Thermal resistance from junction to the bottom of the product case
Thermal Considerations
The LTM8057 output current may need to be derated if it
is required to operate in a high ambient temperature. The
amount of current derating is dependent upon the input
For increased accuracy and fidelity to the actual application,
many designers use FEA to predict thermal performance.
To that end, the Pin Configuration section of the data sheet
typically gives four thermal coefficients:
θJCtop: Thermal resistance from junction to top of the
product case
θJCboard: Thermal resistance from junction to the printed
circuit board.
While the meaning of each of these coefficients may seem
to be intuitive, JEDEC has defined each to avoid confusion and inconsistency. These definitions are given in
JESD 51-12, and are quoted or paraphrased as follows:
θJA is the natural convection junction-to-ambient air
thermal resistance measured in a one cubic foot sealed
enclosure. This environment is sometimes referred to
as still air although natural convection causes the air to
move. This value is determined with the part mounted to a
JESD 51-9 defined test board, which does not reflect an
actual application or viable operating condition.
θJCbottom is the junction-to-board thermal resistance with
all of the component power dissipation flowing through the
bottom of the package. In the typical µModule converter,
the bulk of the heat flows out the bottom of the package,
but there is always heat flow out into the ambient environment. As a result, this thermal resistance value may
be useful for comparing packages but the test conditions
don’t generally match the user’s application.
8057fa
14
For more information www.linear.com/LTM8057
LTM8057
APPLICATIONS INFORMATION
θJCtop is determined with nearly all of the component power
dissipation flowing through the top of the package. As the
electrical connections of the typical µModule converter are
on the bottom of the package, it is rare for an application
to operate such that most of the heat flows from the junction to the top of the part. As in the case of θJCbottom, this
value may be useful for comparing packages but the test
conditions don’t generally match the user’s application.
be inappropriate to attempt to use any one coefficient to
correlate to the junction temperature vs load graphs given
in the product’s data sheet. The only appropriate way to
use the coefficients is when running a detailed thermal
analysis, such as FEA, which considers all of the thermal
resistances simultaneously.
θJCboard is the junction-to-board thermal resistance where
almost all of the heat flows through the bottom of the
µModule converter and into the board, and is really the
sum of the θJCbottom and the thermal resistance of the
bottom of the part through the solder joints and through a
portion of the board. The board temperature is measured
a specified distance from the package, using a two-sided,
two-layer board. This board is described in JESD 51-9.
The blue resistances are contained within the µModule
converter, and the green are outside.
Given these definitions, it should now be apparent that none
of these thermal coefficients reflects an actual physical
operating condition of a µModule converter. Thus, none
of them can be individually used to accurately predict the
thermal performance of the product. Likewise, it would
A graphical representation of these thermal resistances
is given in Figure 4.
The die temperature of the LTM8057 must be lower than
the maximum rating of 125°C, so care should be taken in
the layout of the circuit to ensure good heat sinking of the
LTM8057. The bulk of the heat flow out of the LTM8057
is through the bottom of the module and the BGA pads
into the printed circuit board. Consequently a poor printed
circuit board design can cause excessive heating, resulting in impaired performance or reliability. Please refer to
the PCB Layout section for printed circuit board design
suggestions.
JUNCTION-TO-AMBIENT RESISTANCE (JESD 51-9 DEFINED BOARD)
JUNCTION-TO-CASE (TOP)
RESISTANCE
JUNCTION
CASE (TOP)-TO-AMBIENT
RESISTANCE
JUNCTION-TO-BOARD RESISTANCE
JUNCTION-TO-CASE
CASE (BOTTOM)-TO-BOARD
(BOTTOM) RESISTANCE
RESISTANCE
AMBIENT
BOARD-TO-AMBIENT
RESISTANCE
8057 F04
µMODULE DEVICE
Figure 4
8057fa
For more information www.linear.com/LTM8057
15
LTM8057
APPLICATIONS INFORMATION
3.3V Flyback Converter
350
VOUT
VOUT
3.3V
•
RUN
•
47µF
2.2µF
VOUT–
GND
BIAS
4.7µF
10k
SS
ADJ
LTM8057
MAXIMUM OUTPUT CURRENT (mA)
VIN
VIN
9V TO 15V
Maximum Output Current vs VIN
8057 TA02a
300
250
200
2kV AC ISOLATION
9
11
10
12
VIN (V)
13
14
15
8057 TA02b
2.5V Flyback Converter
VOUT
2.5V
•
RUN
3.1V
100µF
•
2.2µF
GND
–
VOUT
BIAS
4.7µF
12.4k
SS
ADJ
LTM8057
500
MAXIMUM OUTPUT CURRENT (mA)
VOUT
VIN
VIN
3.1V TO 31V
Maximum Output Current vs VIN
8057 TA03a
400
300
200
100
0
2kV AC ISOLATION
0
4
8
12
16
20
24
28
32
VIN (V)
8057 TA03b
8V Flyback Converter
250
VOUT
VOUT
8V
•
RUN
•
2.2µF
22µF
VOUT–
GND
BIAS
4.7µF
4.53k
SS
ADJ
LTM8057
2kV AC ISOLATION
8057 TA04a
MAXIMUM OUTPUT CURRENT (mA)
VIN
VIN
9V TO 15V
Maximum Output Current vs VIN
200
150
100
9
10
11
12
VIN (V)
13
14
15
8057 TA04b
8057fa
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For more information www.linear.com/LTM8057
LTM8057
PACKAGE DESCRIPTION
Pin Assignment Table
(Arranged by Pin Number)
PIN FUNCTION PIN FUNCTION PIN FUNCTION PIN FUNCTION PIN FUNCTION PIN
B1
VOUT–
C1
D1
E1
GND
F1
A1
VOUT–
–
–
A2
VOUT
B2
VOUT
C2
D2
E2
GND
F2
A3
VOUT–
B3
VOUT–
C3
D3
E3
GND
F3
B4
VOUT–
C4
D4
E4
GND
F4
A4
VOUT–
B5
VOUT–
C5
D5
E5
GND
F5
A5
VOUT–
B6
VOUT
C6
D6
E6
GND
F6
A6
VOUT
B7
VOUT
C7
D7
E7
GND
F7
A7
VOUT
FUNCTION
RUN
GND
GND
GND
GND
PIN
G1
G2
G3
G4
G5
G6
G7
FUNCTION PIN FUNCTION
VIN
H1
VIN
VIN
H2
VIN
H3
GND
H4
GND
GND
H5
BIAS
GND
H6
SS
ADJ
H7
GND
PACKAGE PHOTO
8057fa
For more information www.linear.com/LTM8057
17
4
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection
of itsinformation
circuits as described
herein will not infringe on existing patent rights.
For more
www.linear.com/LTM8057
2.540
SUGGESTED PCB LAYOUT
TOP VIEW
1.270
PACKAGE TOP VIEW
0.3175
0.000
0.3175
PIN “A1”
CORNER
E
1.270
aaa Z
2.540
Y
4.445
3.175
1.905
0.635
0.000
0.635
1.905
3.175
4.445
D
X
4.7625
4.1275
aaa Z
SYMBOL
A
A1
A2
b
b1
D
E
e
F
G
H1
H2
aaa
bbb
ccc
ddd
eee
b1
DETAIL A
BALL DIMENSION
PAD DIMENSION
BALL HT
NOTES
DETAIL B
PACKAGE SIDE VIEW
MAX
5.12
0.70
4.42
0.90
0.66
DIMENSIONS
NOM
4.92
0.60
4.32
0.75
0.63
11.25
9.0
1.27
8.89
7.62
0.32
4.00
A
A2
SUBSTRATE THK
0.37
MOLD CAP HT
4.05
0.15
0.10
0.20
0.30
0.15
TOTAL NUMBER OF BALLS: 38
0.27
3.95
MIN
4.72
0.50
4.22
0.60
0.60
H1
SUBSTRATE
A1
ddd M Z X Y
eee M Z
DETAIL B
H2
MOLD
CAP
ccc Z
Øb (38 PLACES)
// bbb Z
(Reference LTC DWG # 05-08-1925 Rev B)
Z
18
Z
BGA Package
38-Lead (11.25mm × 9.00mm × 4.92mm)
F
e
7
5
4
3
2
PACKAGE BOTTOM VIEW
6
1
DETAIL A
H
G
F
E
D
C
B
A
PIN 1
DETAILS OF PIN #1 IDENTIFIER ARE OPTIONAL,
BUT MUST BE LOCATED WITHIN THE ZONE INDICATED.
THE PIN #1 IDENTIFIER MAY BE EITHER A MOLD OR
MARKED FEATURE
BALL DESIGNATION PER JESD MS-028 AND JEP95
TRAY PIN 1
BEVEL
COMPONENT
PIN “A1”
6
!
BGA 38 0517 REV B
PACKAGE IN TRAY LOADING ORIENTATION
LTMXXXXXX
µModule
PACKAGE ROW AND COLUMN LABELING MAY VARY
AMONG µModule PRODUCTS. REVIEW EACH PACKAGE
LAYOUT CAREFULLY
5. PRIMARY DATUM -Z- IS SEATING PLANE
4
3
2. ALL DIMENSIONS ARE IN MILLIMETERS
6
SEE NOTES
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994
b
3
SEE NOTES
G
LTM8057
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/product/LTM8057#packaging for the most recent package drawings.
8057fa
3.810
3.810
LTM8057
REVISION HISTORY
REV
DATE
DESCRIPTION
A
07/17
Connected RUN pin to VIN in Typical Application circuit example
PAGE NUMBER
16, 20
8057fa
For more information www.linear.com/LTM8057
19
LTM8057
TYPICAL APPLICATION
Maximum Output Current vs VIN
12V Flyback Converter with Low Noise Bypass
VOUT
VOUT
12V
•
RUN
•
2.2µF
3.1V
GND
10µF
VOUT–
BIAS
4.7µF
6.19k
SS
ADJ
LTM8057
8057 TA05a
MAXIMUM OUTPUT CURRENT (mA)
VIN
VIN
3.1V TO 24V
200
150
100
50
0
2kV AC ISOLATION
0
5
10
15
VIN (V)
20
25
8057 TA05b
DESIGN RESOURCES
SUBJECT
DESCRIPTION
µModule Design and Manufacturing Resources
Design:
• Selector Guides
• Demo Boards and Gerber Files
• Free Simulation Tools
µModule Regulator Products Search
Manufacturing:
• Quick Start Guide
• PCB Design, Assembly and Manufacturing Guidelines
• Package and Board Level Reliability
1. Sort table of products by parameters and download the result as a spread sheet.
2. Search using the Quick Power Search parametric table.
TechClip Videos
Quick videos detailing how to bench test electrical and thermal performance of µModule products.
Digital Power System Management
Linear Technology’s family of digital power supply management ICs are highly integrated solutions that
offer essential functions, including power supply monitoring, supervision, margining and sequencing,
and feature EEPROM for storing user configurations and fault logging.
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTM8058
2kVAC 1.5W Isolated µModule Converter with 3.1V ≤ VIN ≤ 31V; 1.2V ≤ VOUT ≤ 12V; 20µVRMS Output Ripple
LDO Post Regulator
LTM8031
Ultralow EMI 1A µModule Regulator
EN55022 Class B Compliant, 3.6V ≤ VIN ≤ 36V; 0.8V ≤ VOUT ≤ 10V
LTM8032
Ultralow EMI 2A µModule Regulator
EN55022 Class B Compliant, 3.6V ≤ VIN ≤ 36V; 0.8V ≤ VOUT ≤ 10V
LTM8033
Ultralow EMI 3A µModule Regulator
EN55022 Class B Compliant, 3.6V ≤ VIN ≤ 36V; 0.8V ≤ VOUT ≤ 24V
LTM4612
Ultralow EMI 5A µModule Regulator
EN55022 Class B Compliant, 5V ≤ VIN ≤ 36V; 3.3V ≤ VOUT ≤ 15V
LTM8061
Li-Ion/Polymer µModule Battery Charger
4.95V ≤ VIN ≤ 32V, 2A Charge Current, 1-Cell and 2-Cell, 4.1V or 4.2V per Cell
LTM4613
Ultralow EMI 8A µModule Regulator
EN55022 Class B Compliant, 5V ≤ VIN ≤ 36V; 3.3V ≤ VOUT ≤ 15V
LTM8047
725V DC Isolated µModule Converter
3.1V ≤ VIN ≤ 32V; 2.5V ≤ VOUT ≤ 12V
8057fa
20
LT 0717 REV A • PRINTED IN USA
For more information www.linear.com/LTM8057
www.linear.com/LTM8057
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